Spandex maintains high rubber elasticity, and has excellent physical properties such as tensile stress and recoverability. Therefore, it is widely used in underclothes, socks, sportswear, and the like. These types of spandexes, with their use expanding further, are now also being applied as functional fibers, for instance, for specific applications such as for diapers or as medical fibers, and the like.
Compared to general fibers for medical use, the conventional medical spandex fibers have a higher yarn adhesion between the fiber yarns. This contributes to poor unwinding properties, resulting in many broken yarn during the post-process procedures such as covering, warping, knitting, and the like, and also generates static electricity which causes tension between the yarns to be non-uniform.
Therefore, in an attempt to improve this problem, it is common to add an anti-adhesive to the polymer to enhance the characteristics of the polymer.
The conventionally used anti-adhesives were generally inorganic-based (Mg-st or Ca-st, Zn-st), but these additives are dispersed in the polymer solution without being dissolved therein, thus, there was a problem of the substance not being evenly distributed on the surface of the yarn. Therefore, when these additives were applied in diaper manufacturing problems occurred in the unwinding properties of the spandex.
In order to solve the problems of unwinding properties, and the like, of such spandexes, conventionally, KR 2011-0128884 A proposes an elastic fiber comprising a polyurethane or polyurethane-urea and a soluble anti-adhesive composition of about 0.5 wt. % to 25 wt. %. Here, a cellulose-based composition (CAB) is used as an anti-adhesive.
Further, JP 2001-509877 A, directed to a spandex having low viscosity and a method for producing said spandex, proposes using amides such as ethylene bis-oleylamide/stearamide, etc. containing nitrogen as an anti-adhesive, and CN 001291079 B discloses using antimicrobial substance such as zirconium phosphate, glass and zeolite as an anti-adhesive of spandex.
However, although the anti-adhesive applied in the conventional manufacturing of spandex prevented adhesion between the fiber yarns to a certain extent, it was found that, depending on the addition of the inorganic substance to the anti-adhesive, irregular ballooning and tension spike phenomenon occurring in the unwinding process of the spandex yarn during the diaper manufacturing process were not properly improved. In addition, the above problem is still not solved with an organic-based adhesive agent due to the yarn becoming loose, deterioration of adhesive properties with the hot melt, and compatibility problem with spandex polymer.
Furthermore, in order to improve adhesion with the hot-melt adhesive, there have been cases where an adhesion enhancer was added to an emulsion, or thermoplastic polyurethane or a rosin-based compound and the like was added to the polymer during the production of the spandex fiber. However, when adhesion enhancer was added to the emulsion, there was a problem resulting from non-uniform application on the surface of the yarn due to uneven distribution in the emulsion. Further, when thermoplastic polyurethane was applied to the polymer adhesion did not improve, and when rosin-based compound was added to the polymer there was a problem that the unwinding tension of the spandex fiber became high resulting in inadequate unwinding properties.